Isotope dilution analysis using flow injection inductively coupled plasma mass spectrometry was applied to determine low boron contents in iron and steel samples. Sample dissolution was carried out in a microwave oven with an HCl, HNO3, and H2SO4 acid mixture and high-pressure digestion vessels. A solvent extraction procedure using acetylacetone−chloroform was applied for the separation of the iron matrix as the sulfate (pH = 1.4 ± 0.1). Test solutions corresponding to 50 mg mL-1 of sample, with the total boron content and iron contents below 1 μg mL-1, were obtained. Flow injection was used as a sampling system to minimize problems arising from the total salt concentration of the test solutions. This method made it possible to analyze boron in iron and steel at submicrogram per gram levels. The detection limit (3σ), in micrograms of boron per gram of sample, was 0.02, and the precision for concentrations above 10 times the detection limit was better than 1%. Accuracy was tested with eight standard reference materials with boron certified values in the 0.5−10 μg g-1 range.

ACKNOWLEDGMENT This study forms part of a research project financially supported by the European Community for Steel and Carbon (ECSC) and the Comisio´n Interminesterial de Ciencia y tecnologı´a (CICYT).

Peer reviewed